The present invention relates to a side wall of an ink fountain of a printing machine, comprising at least two plates fixed some distance apart, and an intermediate plate having a front edge in the shape of an arc of a circle mounted between said plates in such a way that it can be moved and tilted, and press means acting on said intermediate plate.
The present invention also relates to an ink fountain for a printing machine comprising at least one side wall according to the present invention. Such walls and ink fountains are known in the state of the art. For example, U.S. Pat. No. 5,230,286, the content of which is incorporated by reference, describes an ink fountain for a printing machine, the side walls of which are in contact with the ink fountain roller to form the radial seal of the ink fountain. In this state of the art, the front edge of the side walls, which has the overall shape of an arc of a circle, does not press effectively against the ink fountain roller except at the ends of the arc of the circle, while that part of the front edge which lies between these ends does not touch the roller, a slot thus formed not, however, being wide enough to allow ink to pass through it.
Nonetheless, it has been found, in use, that this type of seal was not satisfactory. This is because the inks used are often abrasive and therefore merely an imperfect seal is enough for the escaping ink to quickly destroy the seal by wearing away the front edge of the walls which form the seal. In the abovementioned case in particular, the fact that the seal is in contact with the roller only at its ends and not over its intermediate part allows ink to escape through the slot and premature wear of the seal thus occurs.
U.S. Pat. No. 4,991,504, the content of which is incorporated by reference, discloses another ink fountain system comprising partition walls allowing printing with different colors. These partition walls comprise, in particular, two metal plates and an intermediate plate with a front edge in contact with the periphery of the ink fountain roller, producing sealed contact therewith. The metal plates for their part have a plastic bead along their lower edge in order to seal against the partition wall and the bottom of the ink fountain. The drawback of this system lies in the fact that the seal between the intermediate wall and the periphery of the ink fountain roller is not perfect either and that the life of the system is thus limited because of the abrasive properties of the inks which wear away the elements of the system, particularly the intermediate plate.
The purpose of the present invention is to improve the known devices.
More specifically, the object of the present invention is to provide an ink fountain in which the sealing of the side walls is markedly improved, and to do so in a simple manner and at fairly low cost.
Another object of the present invention is to provide a system which can be retrofitted to existing machines, that is to say a system which can be mounted in ink fountains which are already in service without major modification thereto.
These objects are achieved by the features defined in the claims
The side wall according to the invention makes it possible to markedly improve the sealing of the seal and therefore to greatly lengthen its life. On account of its simplicity, the system is easy and inexpensive to produce and can be fitted to machines which are already in operation.